Remote convenience systems are known in the art. One example type of a remote convenience system, known as a remote keyless entry (“RKE”) system, is designed to remotely lock and unlock doors of a vehicle such as a passenger car, SUV, or truck. An RKE system may also control other vehicle functions, such as remote start of the vehicle (useful in areas having cold winter weather), and horn chirp and light flashing (useful for finding your vehicle in a large and crowded parking area). An RKE system will typically include a small portable transmitter, referred to as a fob, carried by the vehicle operator, and a radio receiver installed in the vehicle. Pressing a button on the fob causes the fob to transmit a corresponding coded radio frequency (“RF”) command to the receiver. The receiver decodes the commands and controls vehicle systems so as to complete the commanded action.
It is helpful if the range of the RKE system is rather long so that certain functions (e.g. “remote start” and “vehicle locator” functions) can be initiated from a relatively long distance from the vehicle. U.S. Pat. No. 6,472,999 to Lin describes an RKE system that performs some functions at long distance, and others functions only at much shorter distances.
The range of operation of an RKE system is limited by the power of the RF signal generated by the transmitter in the fob, as well as by the quality of the communication path between the fob and the vehicle. Obstructions (particularly metal obstructions) within the vicinity of the communication path may attenuate the transmitted signal or create so-called ‘multipath’ reflections, either of which may diminish range of operation of the system.